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    Swinging the Arc
    From: Frank Reed CT
    Date: 2004 Dec 5, 16:23 EST
    Does "swinging the arc" the wrong way (as discussed on the list recently) work? That is, are there circumstances under which it will work more-or-less to get the sextant vertical? I suppose the best way to decide would be to try it in practice for various Sun altitudes using three different approaches:
    1) No swing at all. This would serve as a sort of control.
    2) Swinging the arc the "wrong" way by rotating about the line of sight to the horizon. Sun's image moves back and forth across the field of view.
    3) Swinging the "right" way by rotating about the line of sight to the Sun. Sun's image remains essentially centered in the field of view.
     
    For high altitudes, I am nearly certain that method 3 is going to give much better results, but at lower altitudes maybe there isn't much difference. Anyone care to experiment? I also wouldn't be too surprised if method 1 (doing nothing at all --estimating sextant vertical visually) works reasonably well in many cases, too.
     
    Frank R
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
       
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